Field of the Invention
This invention relates to an air/fuel ratio control apparatus for a general-purpose internal combustion engine, particularly to an air/fuel ratio control apparatus for a general-purpose engine using mixed fuel containing alcohol and gasoline.
Description of the Related Art
Conventionally, there is proposed a technique for an engine using mixed fuel containing alcohol and gasoline, which is configured to provide an air/fuel ratio sensor (O2 sensor (oxygen sensor) or a wide-range air/fuel ratio sensor in the exhaust system to detect an air/fuel ratio to determine a deviation from a predetermined value caused due to the mixed alcohol, estimate a rate of the alcohol in the fuel based on the detected deviation of the air/fuel ratio, and determine a fuel injection amount based on one from among sets of characteristics (maps; mapped data) selected from the estimated alcohol rate (or correct the fuel injection amount by the estimated alcohol rate), thereby controlling a fuel injection amount, as taught, for example, in Japanese Laid-Open Patent Application No. Sho 63 (1988)-5131.